1. Technical Field
The present invention relates to a higher order silane composition, a method for manufacturing a film-coated substrate, an electro-optical device, and an electronic device.
2. Related Art
A pattern of a silicon film (an amorphous silicon film, a polycrystalline silicon film, for example) being applied for an integrated circuit, a thin film transistor, and the like is generally formed in such process that after a silicon film is formed on a whole surface of a substrate by a vapor phase process such as chemical vapor deposition (CVD), unnecessary part is removed by photolithography.
However, the method above employs the vapor phase process, so that the method has disadvantages such as necessity for a large-scale device, inefficiency in a material use, difficulty in handling vapor material, and generation of large amount of waste.
Therefore, a method for forming a silicon film by a liquid phase process has been researched, and the following method is disclosed in JP-A-2003-313299, for example. In the method, a higher order silane composition containing a liquid silane compound (cyclopentasilane, for example), a higher order silane compound, and a solvent is applied on a substrate. Then the solvent is removed and a heat treatment is conducted so as to form a silicon film. The higher order silane compound is obtained by irradiating the liquid silane compound with ultraviolet rays so as to photopolymerize the compound. Examples of the solvent include decalin, toluene, decane, octane, xylene, and benzene.
Here, the higher order silane compound has low resolvability with respect to a solvent employed for the higher order silane composition. That is, the solvent employed for the higher order silane composition independently can not solve enough amount of higher order silane compound therein to form a silicon film.
On the other hand, the higher order silane compound is soluble with respect to the liquid silane compound (lower order silane compound), and the lower order silane compound is soluble with respect to the solvent described above.
Therefore, the higher order silane composition disclosed in JP-A-2003-313299 allows a lower order silane compound soluble to the solvent to exist therein as an unreacted substance so as to keep such state that the higher order silane compound is dissolved within the solvent. It can be considered that the higher order silane compound is dissolved in a mixed solvent containing the solvent above and the lower order silane compound, in this higher silane composition.
If a content rate of the higher order silane compound is made high in such the higher order silane composition, a content rate of the lower order silane compound also needs to be made high. However, the lower order silane compound has high oxygen activity and has high vapor pressure, so that the mixed solvent disadvantageously becomes unstable. In order to improve the stability of the mixed solvent, the content rate of the lower order silene compound needs to be made low, but enough amount of higher order silene compound to form a film having a desired thickness can not dissolved in the mixed solvent containing the lower order silane compound in low content rate.
Therefore, development of such solvent that has preferable stability and can dissolve enough amount of higher order silane compound to form a film having a desired film thickness has been required.